Triplex propulsion system and method having thermal radiation suppression aspects



Dec.

R. lM. TRIPLEX PROPULSION BRIDGFORTH, JR SYSTEM AND METHOD HAVING THERMAL RADIATION SUPPRESSION ASPECTS Filed Dec. 12, 1960 MYMMAW ywhat maybe termed a United States Patent O h/lercer Island, Wash., assigner Seattle, Wash., a corporation This invention relates to a propulsion system for reaction v'thrust propelled vehicles such as rockets and, more specifically, to an ultra high energy propulsion system and process characterized by a fuel-oxidizer reaction which autogenously produces a principally non-gaseous reaction productv and the admixture with the reaction product of a low molecular weight gas to serve as a working fluid in converting the thermal energy of the fuel-oxidizer reaction into kinetic energy. In particular, an embodiment of such a system can employ a beryllium or beryllium containing fuel component, oxygen as the oxidizing component, and hydrogen as the working Huid, which constituents provide triplex propellant. In certain aspects, this 'invention also provides a readily controllable propellant system of a type capable of delivering eicient reaction thrust without evidencing substantial thermal radiation from the reactionv exhaust products, thereby greatly increasing the immunity of the system as to detection by thermally sensitive searching and homing devices, it being of course known that conventional high energy propulsion systems are very susceptible in this regard.

The unit of measure of the power of a propellant reaction is theA specific impulse, defined as the thrust of the l rocket engine divided by the lcw'rate of the propellant.

Until the present time, it has been the opinion of those concerned with rocket propellants that the system hydrogen-fluorine gives the highest specilic impulse of any stable chemical rocket propellant. The system of this invention provides a stable chemical rocket propellant with specific impulse substantially greater than that of the hydrogenfluorine system.

Previously, in the selection of rocket propellants, attention has been directed toward those substances which, when reacted together, produce high-temperature exhaust gases. These gases, the reaction products of thevfuel and the oxidizer,y are then expanded through a nozzle to leave the rocket at high velocity and exert a thrust upon the rocket.

Inmy invention the functions of producing heat and of converting thermal energy to kinetic energy are considered separately. Two classes of chemicals are used. One class is called the reactants, and these chemicals involve a fueloxidizer pair which react together to autogenously give a principally non-gaseous, i.e. liquid and/or solid, phase. As will be understood, an autogenously non-gaseous reaction product is one which has a principally non-gaseous phase when generated by the chemical reaction of the fuel-oxidizer pair under the reactionl conditions pertaining in a rocket engine of conventional design. The reactants are selected primarily for their ability to produce large quantities ofheat per unit mass. For purposes of the present invention, beryllium has been found to be the best fuel component and oxygen the best oxidizer component.

The second'class of system constituents is called the working Huid, and is selected primarily for the ability to receive the heat produced by the reactants and, to convert this thermal energy into kinetic energy. For purposes of the' present invention, hydrogen has been found to be the most effective working Huid.

In particular, the reaction Vsystem of the present invention comprises a triplex system involving berylliumoxygen-hydrogen, which components in their intermixture,

chemical reaction, and thermal interaction as a rocket propellant in a rocket engine produce a higher specic impulse than a beryllium-oxygen system, a hydrogenoxygen system, or a hydrogen-ilumine system. 4

In its broader aspects, the present invention comprehends utilization of molecular weight gaseous working iluid with a reaction product which is principally in a non-gaseous phase even in the absence of a working `tuid.

When beryllium reacts with oxygen, beryllium oxide is formed. r[he standard heat of reaction of beryllium with oxygen is the highest of .any fuel-oxidizer pair of elements, being 10,300 B.t.u./lb. at 298 the beryllium oxide is in the solid state and 9,850 B.t.u./lb. if ,the beryllium oxide is in theliquid state. If, however, consideration is given to the hypothetical reaction of beryllium and oxygen at 298 K. to produce beryllium oxide in the gaseous state, then a quite different situation pertains. Instead of large quantities of heat being. evolved, heat is actually absorbed. However, beryllium oxide is in actuality a very nonvolatile substance, and it must be heated to about 4,000 K. in order to develop a vapor pressure of l atmosphere. When beryllium reacts with oxygen in stoichiometric proportions at 1000 p.s.i.a., the majority of the reaction product is present in the liquid phase, with Yonly a small percentage of gas, largely atomic oxygen and atomic beryllium, being present. Now, the prime requisite foran eiective rocket propellant is that it can produce hot gases, which can expand from high pressure to low pressure, producing high velocity gases. Therefore, inspite of the very high heat of reaction of beryllium with oxygen, the beryllium-oxygen system is a very low performance rocket propellant because of the `absence of the necessary amount of gases. The specific impulse `of this system, lunder the conditions deiined with respect to accompanying FIGURE l, with a stoichiometric ratio of oxygen to beryllium, is only 244 lb. f.-sec./ lb. m. Thermodynamic characteristics of this system are shown in the following Table I.

Table 1 [The beryllium=oxygen propellant system-(wt. oxygem/ (Wt. beryllum):1.775. Sea level specic impulse=244 1b. f.:sec./1b. 111.] Y Y Now, when hydrogen is added to the beryllium-oxygen system, suiicient quantities of gas become'available Vso that the expansion process produces high velocities.A There is very little chemical reaction between the hydrogen and the reaction products, and the chemical species present after the reaction has taken place consist VprincipallyofV beryllium oxide in principally non-gaseous phase and hydrogen-in gaseous phase.

low molecular weight of hydrogen, results in a system havingavery high specific impulse. i

The mode by which the tion operates can be explained by referring to the basic principles of mechanics and thermodynamics that describe the flow of gases and' determine the magnitude of the specific impulse. Y Y

31,112,6019? Patentes nec. Je, tees y l an essentially non-reacted, very low ,The very large negative en-l thalpy of formation of beryllium oxide, coupled with the propulsion sysetm of thisinvenv By denition,

iS--speciiic impulse, lb. f.-sec./lb. m.

f :thrust of roel-:et engine, lb.

F at=mass flow rate of propellant, lb. m./sec.

From Newtons law o motion, we have,

where The law o conservation of energy requires that Ve=\/2g](zc-he) (Ill) where J :unit conversion factor, 778 ft.lb. t./B.t.u. lzc=enthalpy in reaction chamber, Btu/lb. rn.; and haz-enthalpy at exhaust plane, B.t.u./ lb. rn.

The specific impulse can be found from the above equations in the following manner:

(l) /zc is @remained-From knowledge of the propellant constituents and their pre-reaction states, the enthalpy of the propellants before reaction is obtained. Since the reaction process in the reaction chamber is adiabatic (ie. without external heat input) and at constant pressure, there is no change in enthalpy and the enthalpy of propellants before reaction equals hc.

(l) Tc is determined- From the equilibrium constants for the chemical reactions which can occur in the reaction chamber, the chemical composition and temperature in the chamber are determined, consistent with the conditions that the enthalpy equals zc as determined under (l) and that the pressure equals Pc, the chamber pressure.

(3) Sc is determined-From a knowledge of Tc, Pc, and the chemical composition, Se, the entropy per unit mass in the reaction chamber is determined.

(4) Te is determined-Since flow in the nozzle is approximately iscntropic, Se, the entropy per unit mass at the exhaust plane, equals Sc. From the equilibrium constants for the chemical reactions which can occur in the nozzle, the chemical composition and temperature at the exhaust plane are determined, consistent with the conditions that the entropy equals Se as determined above and that the pressure equals Pe, the pressure of the exhaust gas at the exhaust plane.

(5) he is determined-From a knowledge of Te and the chemical compositions at the exhaust plane, he is determined.

(6) Is is determined-Prom Equation lll, Ve is determined. From Equations I and ll, ls is determined.

An insight into the various factors which are at work in the breyilium-oxygen-hydrogen system can now be obtained by the following considerations:

For an isentropic expansion process, the first and second laws of thermodynamics require that pJ (IV) where dh=inlinitesirnal change in enthalpy per unit mass,

Btu/lb. 1n.;

dP=infinitesimal change in pressure, lb. f./ft.2; and

p=density, lb. m./ft.3.

Now, approximately,

P=PG

where total mass flow rate of propellant i mass flow rate of gas phase and pG:lensity of gas, lorrL/it From Equations l, ll, lll, and lV, letting Pe=Po, (assuming the ideal gas law) and assuming thermal and ctie equm um between gas phase and condensed phase, we have where nzmoiecular weight of gas phase, lb. rn./ (lb. 1n.mole).

ges

it is evident that for high specic impulse, T should be high, but and M should be low. With the beryllium-oxygen system, the reaction products are largely condensed, with little gas being formed; hence is high, and is is low.

For the purpose of obtaining still more detailed insight into the interactions of the various effects, further assumptions will now be made, leading to approximate equations for specific impulse. Assuming that chemical composition is frozen at chamber conditions, and that specihc heat is independent of temperature, we obtain gin De n'uopM- gcprcii C) l (vr) From Equation V,

where Cp=specilic heat, B.t.u./lb.m.- R. Since CpTc=CpTo+ (l-Z) Qc where To=temperature of reactants and working fluid before reaction in R.;

mass iiow rate of working fluid added to reactants total mass iiow rato through rocret and Qc--heat of reaction of reactants, B.t.u. per lb. m. of reactants, without considering the working uid. This is the heat that would be evolved if 1 lb. m. of reactant were reacted at constant temperature, To, and constant pressure, Pc, to form the chemical composition which would actually obtain under adiabatic reaction conditions.

And, since To is much less than Tc, Equation Vl becomes By cxamming the above equation, the ellects of adding hydrogen as a working luid to a stoichiometric berylliumoxygen reactant system can be seen. As the hydrogen content increases, the following elects occur, considering each term separately:

(l) (l-Zy-rhe factor (1 -Z) decreases, representing a dilution of the heat source. rl`his tends to decrease the speciiic impulse.

(2) QC-With no hydrogen, the majority of the reaction product consists of liquid beryllium oxide, but there also exist small percentagesl of atomic oxygen gas atomic beryllium gas, and still smaller percentages of beryllium oxide gas and diatomic oxygen gas. When hydrogen is added, the beryllium gas and oxygen gas factor Qc, which tends to to lform Vmore* liquid beryllium oxide. With still more hydrogen, the beryllium oxide freezes, and eventually essentially al1 of theberyllium and oxygen in the system are combined in the form of solid beryllium oxide. This results in increase` of the increase Is.

(3) -As hydrogen is added, the beryllium gas and oxygen gas combine and condense, increasing ,8. Soon, however, essentially all vof the beryllium and oxygen are condensed, and addition of more hydrogen causes' to decrease. Ag decrease in causes (R'v/JCpM) to inc'ombine and condense crease, and since (Pc/Pc) is less than l,

becomes less, and hence v gas, with smaller proportions of beryllium oxide gas and diatomicoxygen gas, giving a mean molecular weight of' :approximately l5. When hydrogen is added, the other gases condense, leaving a gas phase composed almost entirely of hydrogen, having a molecular Vweight of ap- .'pr'oximatelyvZ.` This decrease'in M tends to increase Is.

The composite result of all these effects is that as hydrogen is added to beryllium-oxygen, the specific impulseV lirst increases, and then decreases when the hydrogen content is increased above about 27% by weight in the total mixture.

The specilic impulse values out the system berylliumoxygen-hydrogen are shown -in the followingTa-ble II, deining the performance of the propellant at sea level, .and in the following Tables IIVI and IV, deningthe performance of Ithe propellant in the environment of outer space:

Table Il [Specific impulse at sea level-.Beryllium-oxygen-hydrogen., Chamber y pressure=1000 p.s.i.'a.; exit pressure=14-7 p.s.i.a.]

, 6 Table 111 [Specific impulse in vacuum`Berylliiim-oxygen-hydrogen. Chamber pressure=1000hp.s.i.a., (Wt. oxygen)/(Wt. beryllium)=l.775; exhaust nozzle area rat1o=501 Y Specific f Wt. Percent -Hydrogen Impulse,

T able IV [Specific impulse in vacuum-Beryllium-oxygen-hydrogen. Chamber pressure=1000 p.s.i.a.; (wt. oxygem/(wt. beryllium)=1.775. Hydrogen concentration selected for maximum specle impulse) Specific Exhaust Nozzle Area Ratio Impulse,

j lb. f .-sec./1`n.m.`k

VThe following Table lV shows the gains in specific impulse which fthe beryllium-oxygen-hydrogen system produces over the hydrogen-oxygen system yand the hyd-rogen-iiuorine system.

Table V [Berylliurn-oxygen-hyclrogen-Chamber pressureh=l000 p.s.i.a. Pro-r pellant compositions selected for maximum suecnle impulse. Speeltie impulse diterences expressed in lb. f.sec./1b. m.

Increase in Increase in Specific Specific Condition impulse Impulse over over Hydrogen- Hydrogenoxygen Fluorine Sea level; exit pressure=14.7 p.s.1.a 63 48` Vacuum; Nozzle Area Ratio= 82 63 Vacuum; Nozzle Area Ratio=10 82 65 Vacuum; Nozzle Area Ratio=50 92 74. Vacuum; Nozzle Area Ratio 133 165 50 The maximum sea level specific impulse is obtained with the following composition:

A Wt. percent hydrogen=r27 (Wt. oxygen)/(wt. |beryllium )=1.78 As shown in Table Il, this propellant composition gives a sea level specific impulse of 457 lb. f.-sec./lb. m., which is 48 lfb. .-sec./lb. n1.' greater than that of hydrogenuorine, Ithe combination formerly though to be the most powerful stable chemical propellant, which has under the same conditions a specic impulse of 409 lb. -f.sec./ lb. m. It is :also: to *be noted that the sea level specific impulse of the beryllium-oxygen-hydrogen system is 63 lb. f.-sec./lb. m. greater than that of the system hydrogenoxygen, a currently popular high energy propellant which has under the same conditions a specific impulse of 394 lb. f.-sec./1b. m. With large area ratio exhaust nozzles,

greater, approaching up to 133 lb. f.-sec'./ A

lium):1.775, but the concentration of hydrogen for maximum vacuum specific impulse varies from a weight percent of about 25 at a nozzle area ratio of 50 to a weight percent oi about 20 at a nozzle area of 1000, and approaches a weight percent of zero as the nozzle area ratio approaches infinity.

For purposes of ready comparison, and to show the substantially improved performance characteristics of the triplex propellant system here presented, accompanying FlG. l graphically shows the variations oi sea level specific impulse of hydrogen-ilumine and hydrogeni gen systems, as well as that of the beryllium-oxygenhydrogen system of the present invention, assuming a reaction chamber pressure of 1000 p.s.i.a. and an exit pressure of 14.7 p.s.i.a.; FlG. 2 shows a correspondingr comparision of the vacuum specic impulse values ot the three systems under a typical exhaust nozzle area ratio of 50; and FIG. 3 similarly compares the maximum vacuum specific impulses of the three systems at various exhaust nozzle area ratios.

lt is seen from the above tabulated and graphical data that, in the beryllium-oxyge'n-hydrogen propellant system, the relative proportions of the system components are relatively critical for optimum performance and that only combinations within certain ranges are capable of producing specific impulse values which are surliciently great to represent a significant improvement over previous propellant systems.

When the hydrogen content is below about 10% by Weight, the system, although having a specific impulse above that of hydrogen-oxygen at the same hydrogen concentration, has a specilc impulse significantly below that possible with hydrogen-oxygen at higher hydrogen concentrations. When the hydrogen content is raised above about 55% by weight, the over-all propellant density becomes relatively low, requiring heavy tankage, and because of the large diluting effect of the hydrogen, the specific impulse decreases below that of a hydrogenoxygen system. Accordingly, the hydrogen content should preferably be between about and about 40% by weight, for maximum performance, with about 10% as the lower limit of interest and about 55% as the upper limit ot interest.

For stoichiometric reaction between beryllium and oxygen to form beryllium oxide, the ratio (wt. oxygen)/ (wt. beryllium) should be about 1.78. When excess beryllium is added to the system, the oxygen to beryllium ratio falls below 1.78. With very low hydrogen content, the beryllium vaporizes and acts as a working iluid, reducing and increasing speciiic impulse. At larger concentrations of hydrogen, the principal eiect of an excess of beryllium is the absorption of heat in vaporization, reducing the specic impulse. At still larger hydrogen concentrations, the beryllium does not vaporize, but reduces specic impulse due to its eiect in diluting the heat source.

The addition of excess oxygen, above the stoichiometric ratio, produces appreciable quantities of water in the gas phase, reducing the weight percent of condensed phase but reducing the over-all heat of reaction per pound of propellant. With a very large oxygen content, the system approaches the hydrogen-oxygen system, and the presence of small amounts of beryllium in the propellant is unjustied because the comparatively small gain in performance would not normally justify the consequent increase in complexity required to introduce a third component. Therefore, the ratio (wt. oxygen)/ (wt. beryllium) should usually be near stoichiometric, i.e. about 1.78, and the entire range of interest for this ratio extends from about 1.00 to about 30.0.

With respect to the above considerations as to specic propellant formulations, it is of course to be kept in mind that an optimum propellant constituency in a given situation will depend upon the specilic mission whic the rocket system is to perform, and does not always exactly correspond to the composition giving maximum specific impulse. Tank weights must be considered, in a study of the particular mission and the propellant requirements. For some missions, a composition which has a greater over-all propellant density may have lower tank weights and may give better over-all vehicle performance than given by the exact constituency having maximum speciiic impulse. The optimum propellant composition, with the optimum compromise between high specific impulse and high propellant density, therefore depends upon the specific mission and utilization environment.

This propellant system is utilizable in a rocket engine by techniques generally known per se in rocket techinology. Storage chambers are provided for the propellants, which are suitably transported from the storage chambers to the reaction chamber. l-lere, mixing and chemical reaction take place, the beryllium reacting with the oxygen and releasing large quantities of heat. The hydrogen mixes with the beryllium oxide, receives its heat, and expands through a converging-diverging nozzle, carrying along the solid and/or liquid beryllium oxide, and leaving the rocket at high velocity, exerting 4a thrust on the rocket.

The hydrogen and the oxygen can be carried in propellant tanks as liquids, using the technology of handling cryogenic iiuids which is now well developed in the rocket industry. The beryllium can be carried in storage tanks and introduced into the reaction chamber in the form of small pellets or powder, or in the form of wire, bar, paste or slurry with a suitable liquid vehicle such as a hydrocarbon present in minor proportion, which preferably can nominally also react in the fuel-oxidizer reaction. Alternately, the beryllium can be carried directly in the reaction chamber in suitable solid form, such as a chamber liner, and can constituently be either substantially pure or contain relatively small quantities of beryllium hydride or ammonium perchlorate, for example.

The beryllium, oxygen, and hydrogen preferably are injected, exposed, or otherwise introduced to the reaction chamber at essentially uniform rates and in such a manner as to obtain rapid interrnixing of all three. A modication of this method of injection consists in designing the injector so that the beryllium and oxygen are mixed first, and the resulting beryllium oxide is then mixed with hydrogen, which has been injected around the walls at the primary injector or which has been injected downstream of the primary injector station.

In another utilization layout for the system, a portion of the hydrogen is carried in the form of beryllium hydride by having a portion or all of the beryllium in the form of beryllium hydride. In the following Tables VI and VII, it is seen that the specific impulse of the beryllium hydride-oxygen-hydrogen system is not quite as great as the beryllium-oxygen-hydrogen system. However, the over-all density of the propellants is increased and under some circumstances it can be practicably desirable to employ an essentially beryllium hydride, oxygen, and hydrogen system.

Table Vl [Specific Impulse at Sea Levelderyllium Hydritle-Oxygen- Hydrogen, Chamber Pressure-:1000 p.s.i.a.; Exit Prossurezlj p.s.1.a. (Wt. Oxygen)/(WtA Berylliu1n):1.775]

Specific irnpulsc, lb. f.- soe/lb. m.

Wt. Percent Uncornbined Hydrogen given by the equation:

where v; khydrogen lies between about and about 40.

Table VII [Specific Impulse in VacuumBeryllium "Hydride-Oxygen- Hydrogen. Chamber Pressur :1000 p.s.i.a. (Wt.V Oxygen)/(Wt Beryllinm):1.778. Hydrogen Concentration Selected for Maximum Specific Impulse] Specific Impulse, lb. f.-

Exhast Nozzle Area Ratio A see/lb. m.

these viewpoints. K

i Table V111 [Chamber temperature-Chamber pressure=1000 plsifaLLExit pressure v=14.7 p.s.i.a. Concentrations selected for maximum specific impulse] Temperature Propellant m Reaction Chamber, '.F.

Hydrogen-Fluorine 6, 500 Hydrogen-Oxygen n 4, 930 Beryllium0xygon-lydrogen 4, 620

A potential method of detecting the launching of misk siles is by the use of instruments which respond to the radiations emitted Vby the hot exhaust gases from the rocket. The energy which is radiated by hot bodies is where v =energy per unit area per unit time;

- geometry; TL-Stephan-Boltzmann constant; and

*Y e=emissivity, a function of temperature, pressure, and

" T=absolute temperature.

Y Fora specific gas, the above Vequation can be approximated by an'equation of the following type:

Since the exponent of the temperature of the aboveV equations is so high, it is evident that a decrease in the temperature of the radiating gases brings about a very great Vdecrease in the radiant energy which is emitted.

f Thus, a decrease in the temperature of afactor of 3 will reduce the radiated energy to about'l%'of its previous value. It is evident, that with suiliciently cool exhaust gases, the energy radiated by the rocket Will become so low that it will be diflicult to detect, and, eventually, as the temperature is lowered (as by adding more hydrogen, for example), the radiation from the rocket becomes the Same as from the ambient background, and the rocket gases become essentially invisible to infrared detection systems. I

For centain applications, it can be desirable to utilize a propellant having high specific impulse but which provides exhaust products having very low temperatures. lf the temperature -of the exhaust products is only Vslightly above ambient temperature, equal to ambient temperature, or slightly below ambient temperature, the infrared radiation emitted by the exhaust products is decreased `to the point where detection and tracking of avehicle launching and ilight by means of infrared sensors becomes diicult or impossible. For example, a ballistic missile can be launched with all stages employing cool reaction products; or, alternately, the final upper stage only could utilize cool propellants in applying the iinal or burn out velocity of the missile. In this lway, the missile can be rendered substantially invisible toan infrared or like thermally responsive detection system. yIt is an important facet of this invention that the thermal radiation level is readily controllable simply by regulation of the proportionof working fluid mixed with the reaction products. Manifestly, any sequence of regulation can be employed and automatically effected to gain optimum performance (highest specic impulse) or optimum thermal invisibility as desired during llightprogress, depending upon specitic mission requirements. As a furtherramilioaition of the control of the thermal invisibility of 7a reaction propelled beryllium-oxygen-hydrogen Table IX [Exhaust temperature-Beryllilun-oxygen-hydrogen (wt. O/wt. Be=1.775); chamberpressure=1000 p.s.i.a.]

Exhaust Chamber Exhaust Wt. Percent v Temperature, Temperature Telltslre Hydrogen F. Pe=l4-7 p.s.i.a., 'Nozzle Area' F Ratio=5o, F.

50 2, 140 460 7K 55 1, 740 290 y-l01 With conventional propellants, the variation of the mixture ratio to produceveryY low temperature exhaust produots will also produce very low specific impulse, and hence is undesirable froml the standpoint of overall performiance. However, the beryllium-oxygen-hydrogen-system can provide high speciiic impulse at a very low temperature, and the'temperature can be readily controlled by varying the percent of hydrogen, as above indicated.

The striking capability of `a propulsion system involving an essentially unreaoted, very l-ow molecular weight working Huid with the exhaustproducts at about ambient temperature, yet nevertheless obtaining high specific impulse is demonstrated by an inspection of Table IX along with accompanying FIGS.. 1 and 2. When the proportion of the hydrogen constituent is about 50-55%, `,as shown at I`FIGS. l and 2, the `specific impulse of the-system is still directly comparable'to the highest obtainable in hydrogen-iluorine or hydrogen-oxygen propellant systems,

gives two examples of tem-V lln even though the order of exhaust product temperatures is about ambient (Table IX).

It is a further characteristic of this invention, of fundamental importance insofar as concerns providing high specific impulse and substantial thermal invisibility, that the cooling eifect of the very low molecular weight working fluid can be utilized in various other types of propellan-t systems and is by no means limited to the speciiic beryllium-oxygen-hydrogen system here disclosed. For example, similar thermal invisibility is within the capability of the lithium-liuorinc-hydrogen system disclosed in my copending application Serial No. 67,017, liled November 3, 1960, and entitled Triplex Propulsion System and lvlethod, it being of interest also as to the application of this thermal invisibility concept to a lithium-duermehydrogen system that its reaction products can be characterized as of a type having an autogenously gaseous hase and that the cooling effect of the hydrogen in that environment is also not inconsistent with high speciiic irnpulse. Other propellant systems wherein a very low molecular weight working fluid can be proportioned to give substantial thermal invisibility, such as boron (or boron hydride)-lluorine-hydrogen, and boron (or boron hydnide)-oxygenhydrogen systems. Yet other systems of like functionality in this respect will occur to those skilled in the art to which the invention is addressed.

The specilic impulse values reported in this speciiication apply to the case of isentropic `and equilibrium flow and are based upon the propellants in the following initial states: liquid para hydrogen at its normal boiling point of 20 l.; liquid oxygen at `its nor-mal boiling point of 90 K.; solid beryllium at 298 K.; and solid beryllium hydride at 298 K. Y

The above principles with 'respect to utilization of a very low molecular weight working iluid to improve thermal invisibility can also be applicable to other reaction engines such as ramjets and turbojet-afterburner combinations to momentarily decrease exhaust temperatures and rence decrease infrared radiation when needed, as when a craft is under attack by a thermally homing intercept missile. For example, hydrogen from a standby source can be injected on an emergency basis at the afterburner stage of a turbojet engine to cool the reaction and reduce exhaust temperature.

From the foregoing specification it is seen that there is present a beryllium-oxygen-hydrogen rocket propulsion system, which triplex system is characterized essentially by a chemical reaction between a beryllium containing constituent and oxygen, producing an essentially beryllium oxide reaction product which is autogenously in principally non-gaseous phase, and with the hydrogen acting as a low molecular weight expansion gas, i.e. working fluid, functioning to efficiently convert the thermal energy available from the non-gaseous phase reaction product into kinetic energy, producing a high specific impulse. lt is also seen that certain aspects of the invention realize significant reduction in relative infrared radiation, and that such aspects of the invention are or' broader application than the specific propulsion systems here disclosed.

From the foregoing considerations, various further modications, formulations, and utilization techniques characteristic of the invention will be apparent to those skilled in the art, within the scope of the following claims.

What is claimed is:

1. The method of generating high specific impulse in a reaction engine having beryllium oxide reaction chamber and a discharge nozzle and utilizing a fuel-oxidizer reaction producing a reaction product which is essentially beryllium oxide; said method comprising mixing essentially unreacted hydrogen with said beryllium oxide reaction product in said chamber in sulilcent amount to materially increase specific impulse by reducing average molecular weight and by converting a substantial part of the thermal energy of the chemical reaction into kinetic energy as the mixture discharges from said nozzle.

2. A. high specific impulse propellant composition, comprising fuel and oxidizer reaction components forming a reaction product which is essentially beryllium oxide, such propellant composition further comprising essentially unreacted hydrogen admixed with such reaction product to convert a substantial portion of the heat of reaction into kinetic energy.

3. The propellant composition of claim 2, wherein said fuel component is selected from the group consisting of beryllium, beryllium hydride, and mixtures thereof.

4. The propellant composition of claim 2, wherein said oxidizer component is essentially oxygen.

5. The method of generating ultra high energy reaction propulsion comprising reacting a beryllium containing fuel component with oxygen, such reaction occurring in a reaction chamber having a high area ratio exhaust nozzle and occurring in the presence of essentially uncombined hydrogen, the propulsion producing mass having present therein autogenously reacted beryllium oxide, and also having present sufficient essentially uncombined hydrogen to constitute at least about ten percent by weight of the total weight of the propulsion producing mass.

6. A method of generating thrust in a rocket engine; said method comprising mixing beryllium, oxygen and uncombined hydrogen in a reaction chamber, and discharging the beryllium oxide reaction product and admixed hydrogen through an exhaust nozzle at high velocity, producing thrust; the weight ratio of oxygen to beryllium being between about 1 and about 30; and the weight percent of the uncombined hydrogen in the discharging mixture being between about 10 percent and about 55 percent.

7. A method of generating thrust in a rocket engine; said method comprising mixing beryllium, oxygen and uncombined hydrogen in a reaction chamber, and discharging the beryllium oxide reaction product and admixed hydrogen through an exhaust nozzle at high velocity, producing thrust; the weight ratio of oxygen to beryllium being approximately 1.78, and the weight percent of the uncombined hydrogen in the discharging mixture being between about 20 percent and about 40 percent.

8. A method for generating thrust in a rocket engine; said method comprising mixing beryllium hydride, beryllium, oxygen and uncombined hydrogen in a reaction chamber and discharging the beryllium oxide reaction product and admixed hydrogen through an exhaust nozzle at high velocity, producing thrust; the weight ratio of oxygen to total beryllium being approximately 1.78, and the weight percent of the uncombined hydrogen in the discharging mixture being between about 10 percent and about 40 percent.

9. The method of rocket propulsion comprising: exothermally reacting in a propulsion reaction chamber fuel and oxidizer components characterized by the formation of an at least primarily non-gaseous reaction product; and non-reactively admixing uncombined hydrogen with the reactant components in suilicient amount to produce high propulsion performance.

10. The method of rocket propulsion comprising: exotherrnally reacting in a propulsion reaction chamber fuel and oxidizer components characterized by the formation of a reaction product which is at least primarily nongaseous; and non-reactively admixing uncombined hydrogen with the reactant components in sufficient amount to produce high propulsion performance with minimal thermal radiation from the rocket exhaust.

1l. The method of rocket propulsion comprising; exothermically reacting in a propulsion reaction chamber fuel and oxidizer components generating a reaction product having a substantially higher heat per unit mass than is generated by stoichiometric reaction of oxygen and hydrogen; and non-reactively admixing uncombined hydrogen with such reaction product in suilicient amount to effectively cool the reaction product to about the temperature of the ambient environment as it exhausts from said t 14 t Y reaction chamber, the cooled reaction product neverthe- References Cited n thefile ofthis patent iess providing high propulsion performance while exhaust- UNITED STATES PATENTS mg from the reaction chamber. 12. The method of claim 11, further comprising sens- 218111431 Zwicky et al' Oct- 29' 1957 ing the temperature of the ambient environment, and 5 2956402 Rae Oct' 18' 1960 regulating the proportion of hydrogen admixed with the reaction'product in response to the temperature of the ambient environment.

3,040,518 R-ae Q June 126, 1962 

1. THE METHOD OF GENERATIG HIGH SPECIFIC IMPULSE IN A REACTION ENGINE HAVING BERYLLIUM OXIDE REACTION CHAMBER AND A DISCHARGE NOZZLE AND UTILIZING A FUEL-OXIDIZER REACTION PRODUCING A REACTION PRODUCT WHICH IS ESSENTIALLY BERYLLIUM OXIDE; SAID METHOD COMPRISING MIXING ESSENTIALLY UNREACTED HYDROGEN WITH SAID BERYLLIUM OXIDE REACTION PRODUCT IN SAID CHAMBER IN SUFFICIENT AMOUNT TO MATERIALLY INCREASE SPECIFIC IMPULSE BY REDUCING AVERAGE MOLECULAR WEIGHT AND BY CONVERTING AQ SUBSTANTIAL PART OF THE THERMAL 